This invention relates generally to windmills and more particularly has reference to yaw and speed control devices for horizontal axis windmills.
An upwind horizontal axis windmill has the mill facing into the wind. The mill is pivoted about a vertical axis so that it can be aligned to always face into the wind. However, such a windmill is inherently unstable. The mill blades tend to swing to the downward side unless some means of alignment is provided.
The traditional upwind mill has a long tail sail which puts the center of wind behind the pivot. That produces a force to turn the mill into the wind which is greater than the force produced by the mill rotor to turn the mill away from the wind. A typical example is the water pumping windmill seen throughout the Midwest. It has a vertical axis pivot just behind the mill rotor and a long tail sail boom to provide relatively stable alignment. However, tail boom sails become unwieldly and unsightly on large windmills and are thus undesirable.
A technique commonly used in modern windmills to overcome that problem is to abandon the upwind approach and make the windmill a downwind mill by letting the mill blow around to the downwind side. Such mills usually have a thin tower which the wind can easily blow through to strike the lower rotor blades.
However, upwind mills are more desirable because they are more efficient. A technique used in modern upwind mills is to servo-control the windmill to align it with the wind. This technique is also used on downwind machines. A separate wind direction sensor is used to drive a servo-system which aligns the mill with sensor. Some wind direction sensors, especially those used on downwind machines, are mounted on the windward side of the mill machinery cap. However, that mounting is impractical for upwind machines because of wind distortion caused by the mill rotor. Hence, upwind mills generally use a sensor mounted a distance from the windmill sufficient to be relatively free from wind distorting effects. However, such a system often has alignment errors caused by variations in wind direction between the windmill site and the site of the wind direction sensor.
Pertinent United States and foreign patents are found in Class 60, Digest 2; Class 290, Subclass 55; Class 318, Subclasses 652, 656, 671 and 673; and Class 416, Subclasses 9, 10, 37, 40, 41, 44, 51, 139 and Digest 2 of the Official classifications of patents in the U.S. Patent and Trademark Office.
Examples of pertinent patents are U.S. Pat. Nos.: 329,914; 390,698; 401,867; 1,633,460; 3,942,026; 2,563,279; 3,032,119; 3,902,702; 4,088,352.
French Pat. No. 2,355,178 is also pertinent.
U.S. Pat. Nos. 329,914; 390,698; 401,867; 1,633,460 and 3,942,026 disclose windmills that are aligned with wind by mechanical means.
U.S. Pat. Nos. 2,563,279; 3,032,119; 3,902,072 and 4,088,352 disclose wind power plants that are aligned by mechanical or electrical means. A wind vane device is used for positional movement.
French Pat. No. 2,355,178 shows an electrical system used in conjunction with a large spur gear turntable.
From the foregoing, it is clear that a need exists for a compact device which can continuously provide accurate alignment of an upwind horizontal axis windmill. The prior art devices have proved unsatisfactory.
Small windmills traditionally are provided with brakes, governors or shutdown devices which crudely regulate rotor speed. Most large windmills use servo-controlled variable pitch mechanisms which adjust the blade angle of attack to keep the speed constant.
Pertinent U.S. and foreign patents are found in Class 416, subclasses 23, 44, 47, 48, 50, 51, 52 and 53 of the Official Classifications of patents in the U.S. Patent and Trademark Office.
Examples of pertinent patents are U.S. Pat. Nos.: 260,096; 438,251; 802,747; 910,701; 965,387; 1,422,602; 1,542,433; 1,633,428; 1,776,211.
U.S. Pat. Nos. 802,747; 965,387 and 1,422,602 illustrate fliud reaction surfaces that are pivotally controlled to regulate rotor speed. The vanes are controlled by control rods and bars.
U.S. Pat. Nos. 260,096; 438,251 and 1,542,433 disclose wind engines with speed control. The movement of vanes is regulated and adjusted by connecting rods.
U.S. Pat. Nos. 910,701; 1,633,428 and 1,776,211 disclose windmills that are speed regulated by pivoting wind vanes. The vanes are connected to control rods which allow for uniform control.
The following patents are also of interest, but are less relevant than those described above: U.S. Pat. Nos.: 244,677; 478,945; 1,648,837; 1,670,099; 1,713,866; 1,826,039; 2,067,542; 3,891,347; 4,111,601.
Although several patents show windmill blades having plural pivotable panels connected to a control rod for simultaneous operation, most use relatively complex governor-controlled linkages to adjust the panels for speed control. The need exists for a non-complex speed control device.